Spark advance for magnetos



SPARK ADVANCE FOR MAGNETOS Filed March 25, 1936 Patented Mar. 23, 1937UNITED STATE FATENT OFFl William 0. Bechman, Chicago, Iil., assignor toInternational Harvester Company, a corporation of New Jersey ApplicationMarch 23, 1936, Serial No. 70,250

4 Claims.

This invention relates to a spark advance device for ignition timers.More specifically, it relates to an adjusting device for ignition timersincorporating a positive limit in the advancing 5 of the spark, wherethe magneto has more advance than is required on different engines. Thismechanism makes it unnecessary to have special magnetos as far as thestop in the breaker is concerned and makes it possible to use a standardmagneto. It is customary to provide a mounting for the breakerassemblies of ignition timers, which will permit of angular movementthereof relative to the shaft on which the timing cam is located. Bythis means, the time at which a spark is delivered may be advanced orretarded.

The principal object of the present invention is to provide an improvedlinkage of a simplified construction for angularly adjusting ignitiondevices, which incorporates a positive stop against spark advance beyonda predetermined limit determined by the construction of the advancinglinkage.

Figure 1 is a plan view of a housing on which an ignition device ismounted, showing the advance device of the invention as embodied on amagneto of conventional construction;

Figure 2 is an end elevation of the structure shown in Figure 1, with aportion broken away by a vertical section to show the breaker assembly;and,

Figure 3 is a section on the line 33 of Figure 2.

In the drawing, a portion ID of a magneto frame is shown. A magneto ofthis type is shown in the Borgerd et a1. Patent No. 1,999,030 of April23, 1935. Particularly when used with tractors, the ignition breaker isusually mounted directly at one end of the magneto, timing beingaccomplished by the magneto shaft. A

casing H is secured to the magneto frame it by cap screws l2, l3, and M.The casing H is provided with an annular flange l5, best shown in Figure3, which provides a bore [6 into which the breaker cup I! is rotatablyfitted for angular movement about an axis concentric with the axis ofthe magneto shaft IS. The breaker cup ii and the breaker assemblycarried thereby is of a conventional construction, as shown in theBorgerd et a1. Patent No. 1,982,463 of November 27, 1934. A

breaker arm l9, which carries a rubbing block 20, is pivotally mountedon a shaft 2i. The breaker arm carries a contact point 22, which ispositioned to engage a stationary contact point 23 carried by a bracketsupport 24. Said support is adjustably mounted on the breaker cup by acap screw 25. The shaft l8 carries a cam 26 operative to engage therubbing block it and separate the breaker points 22 and 23.

At its upper edge, the breaker cup 5? is provided with two spacedinturned flanges 2i. These flanges provide driving means for annularadjustment of the cup.

A cover '23 rotatably fitted over the flange i5 carries a driving lug 29extending downwardly between the flanges 2?, whereby the cover and thecup rotate together.

As best shown in Figure 1, the cap screw l3 carries an extension onwhich a spring member 39 is pivotally mounted for engagement with thecenter portion of the cover 28. Said member removably holds the cover inposition for annular movement.

The cover 28 is provided with an adjusting arm 3i formed integrallytherewith. Said arm eX- tends laterally from the cover. A bolt 32extends through an opening 33 formed in the adjusting arm 3| and isrigidly secured thereto by nuts 34 positioned at either side of theadjusting arm.

An adjusting member 35 of a general L-shape is pivotally mounted at theshort portion of the L on an extension of the cap screw Id. Theadjusting member is freely movable axially oi the pivot forming portionof the cap screw to provide for easy removal with the cover 28.

The member 28 is provided with a slot 36 extending closely adjacent thepivoted end toward the long portion of the L. Said slot forms a meansfor adjustably connecting the member to the bolt 32. Washers 37 oneither side of the member 35, a spring 38 surrounding the bolt 32, and anut 39 threaded thereon provide means for frictionally maintaining themember 35 in position at right angles to the bolt 32.

In the operation of the device as above described, the breaker cup I6 isrotated in a clockwise direction, as indicated by the arrow in Figure 2,for advancing the occurrence of the spark. This advance is secured byrotating the cover by means of the adjusting member 35. When the maximumposition of advance is reached, as illustrated by the adjusting memberposition shown in Figure 2, the bolt reaches the end of the slot 35,thereby providing a positive stop against further advance. To retard thespark, the member 35 is moved toward the position shown by dotted 1lines in Figure 2. By this movement, the adjusting arm 3| of the cover28 is moved in an anticlockwise direction. During this movement, thebolt 32 moves along the slot 36 with the friction washers 3'! slidingalong the portion of the i member adjacent the slot. The friction meansprovided by the washers 31, the spring 38, and the nut 39 maintain theadjusting member in any of its positions of spark advance. Anotherimportant feature of this construction is that the cover 28 may beremoved without interference caused by the provision of the adjustingmechanism, as said mechanism is removed with the cover. The pivotedportion of the member slides axially over the pivot forming portion ofthe screw l9.

Although applicant has shown and described only a preferred embodimentof his improved spark advance device as applied to a magneto timer, itis to be understood that he claims as his invention all modificationsthereof falling within the scope of the appended claims.

What is claimed is:

l. A spark advance device for ignition timers which comprises incombination with an ignition breaker mounted for limited angularmovement, an adjusting arm extending radially from the breaker, anadjusting member pivotally mounted on an axis parallel to the axis ofthe breaker, said arm, being provided with a slot extending on a radiusextending through its pivot axis, and a pin extending through theactuating arm and through said slot, said slot being formed to provide astop against rotation of the breaker When a predetermined maximum sparkadvance is reached.

2. A spark advance device for ignition timers which comprises incombination with a housing, an ignition breaker rotatably mountedtherein, a breaker cam rotatably mounted in the breaker, an adjustingarm extending radially from the breaker and connected thereto, anadjusting member pivoted to the housing on an axis parallel to the axisof the breaker adjacent to the periphery thereof, said arm beingprovided with a slot extending on a radius extending through its pivotaxis, and a pin extending through the actuating arm and through saidslot, said slot being formed to provide a stop against rotation of thebreaker when a predetermined maximum spark advance is reached.

3. A spark advance device for ignition timers which comprises incombination with an ignition breaker mounted for limited angularmovement, a cover for the breaker mounted for angular movementtherewith, an adjusting arm extending radially from the breaker, anadjusting member pivotally mounted on an axis parallel to the axis ofthe breaker, said arm being provided with a slot extending on a radiusextending through its pivot axis, and a pin extending through theactuating arm on the cover and through said slot, said slot being formedto provide a stop against rotation of the cover and the breaker carriedthereby When a predetermined maximum spark advance is reached.

4. A spark advance device for ignition timers which comprises incombination with a housing, an ignition breaker mounted for limitedangular movement in the housing, a breaker cam rotatably mounted in theignition breaker, a cover for the breaker mounted for angular movementon the housing concentrically with the breaker, means forinterconnecting the breaker and cover for angular movement together, anadjusting arm extending radially from the cover, an adjusting memberpivoted to the housing on an axis parallel to the axis of the coveradjacent the periphery of said cover, said arm being provided with aslot extending on a radius extending through its pivot axis, and a pinextending through the actuating arm on the cover and through said slot,said slot being formed to provide a stop against rotation of the coverand the breaker carried thereby when a predetermined maximum sparkadvance is reached.

WILLIAM O. BECHMAN.

